Assigning shape key to a curve
Found the answer here:
https://blenderartists.org/t/blender-add-on-to-import-shape-keys-from-youtube/1124990
Here's the add-on that does this:
https://youtu.be/XMimQfQR_ss 
As per the suggestion in the comment, here's the brief description:
The add-on descried in the video above imports svg paths directly as shape keys. So if I have a rectangle and circle in the svg file and if I group them with rectangle at the top in the xml group, circle will be imported as shape key and rectangle as the target. Apparently, there are no limitations about the number of nodes, as texts can also be imported as a shape key. There can be many shape keys for one target.
Download link: https://github.com/Shriinivas/shapekeyimport